DE2310103A1 - ELECTRONIC OVERCURRENT RELEASE - Google Patents

Description

Licentia Patent-Verwaltungs-GmbH

6 Frankfurt / Main, Theodor-Stern-Kai 1

SGN-72/22 Frankfurt / Main, February 28, 1973 Wei / hs

Electronic overcurrent release

The invention relates to an electronic overcurrent release for protecting motors and cables etc. for the cooperation rait well-known power switching elements such as contactors, circuit breakers and the like.

To protect motors, cables, systems, etc., the well-known power switching elements - such as contactors, Circuit breakers, motor protection switches and the like are equipped with over-current releases or work to-

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at least with such. An essential common thing A characteristic of all these release devices is a release time behavior that is inversely proportional to the monitored one Electricity is. Some devices of this type also contain other functions such as the quick release of the short circuit and the differential release, the one Triggering in the event causes the differences in the current level in the individual phases to be a certain Exceed amount.

In addition to the known solutions on bimetal and electromagnetic Recently, more and more electronic solutions have come onto the market. With these Facilities will trigger behavior by irr. essential analog acting electronic devices caused. For example, the current-inverse tripping time behavior by integrating the current square with simultaneous return of the integrated value to one so-called "integrating amplifier" are effected. However, there are a number of such solutions, which act analogously of disadvantages. One of the main problems is long-term stability To achieve them, special effort is required. Also need to achieve the time behavior, relatively large and therefore expensive capacitors and other components are used. Until now it has not been possible to find such a device for small conventional overcurrent releases to manufacture competitive price.

The invention is based on the object of an electronic To create overcurrent release of the type described above, which on the one hand works very precisely, on the other hand can also be produced without the effort described. According to the invention this is achieved by that a digital circuit is available, which in case of overcurrent causes a deployment decision. With a digital circuit the behavior of overcurrent -

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triggers can be digitally reproduced. For this purpose, for example, the logic structure of the digital circuit can be designed as a microcomputer, ie it contains a control unit, some data memories, an arithmetic unit and an INPUT and OUTPUT device. Furthermore, the digital circuit can be constructed in the form of a counter which simulates the temperature of the overcurrent protection device to be simulated in that its counter reading is counted upwards proportionally to the current level and downwards proportionally to the temperature. Highly integrated electronic circuits can be used as components for these arrangements, which are constructed, for example, in so-called "MOS" or J ¹ TTL "technology. MOS and TTL mean:" metal-oxide circuit logic "or" transistor -Transistor-Logic ". Finally, instead of a special digital circuit, a corresponding circuit of an existing computer can be used, so that the overcurrent release then only consists of the input and output elements.

The idea of the invention is explained in more detail below:

In the simplest case, the heating behavior of a standard overcurrent release can be determined by the following differential equation to be discribed:

T is the time constant, V ^{1 is} the temperature and the final temperature that is established for a given current after an infinitely long time. If you write the differential equation as a difference equation and transform it somewhat, you get:

Ci)

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the well-known relationship, according to which the change is proportional to the distance from the final value to be reached ifc »v. For calculating of a new value of the temperature in a digital computer, the change in temperature will now be the old value added. If this is carried out, the following results for the new value of the temperature in relation to the old value Equation:

_(J )

With this relationship, the behavior of an overcurrent release can be digitally simulated perfectly. With a suitable choice of the step size A1, for a given time constant T, the constant (SX / Ύ can be selected in such a way that the required multiplication with the respective temperature value is reduced to a simple position shift. If, for example, ** f ~ J - 0.001 is selected, the result is The following scheme is used to calculate the new temperature value

This means that the entire amount of calculation required to calculate the new temperature value can be simply shifted and adding or subtracting reduced.

To explain the function and structure of the subject of the application Reference is made to the drawing in which a flow chart is shown in FIG. In Fig. 2 shows a computer configuration. Fig. 3 shows the arrangement of the invention in cooperation with a Switching device. A counter configuration is shown in FIG.

A complete computing cycle is carried out in the The flowchart of FIG. 1 is explained. The one from the analog

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The instantaneous value of the current provided to the digital converter 1 is transferred in digital form to the input register 2 for the current. In the simplest case, the final temperature is assumed to be proportional to the value of the current, then the actual calculation step according to formula (3) can be carried out immediately, - Subsequently, it is checked in 3 whether the new temperature has exceeded the trigger temperature; if not, a new computing cycle is initiated with the return to input register 2; if it does, a trip command is given via the command generator k and the program then returns to the input register 2 for the current. It is assumed that the trip command results in the current being switched off and the input register thus receiving the value O from the analog-digital converter. The flow chart described then also perfectly simulates the cooling process.

A possible configuration of a computer for the present The task is shown in FIG. By means of a clock generator 11, which in the simplest case is derived from the network frequency can consist, the individual steps of the calculation process are from a program memory 12 in cyclic order by means of the subsequent link / to the other units of the work given. In its middle part, this consists of an adder 1d with an accumulator 15 as well as two further registers l6 and 1? to save the current temperature value and to save it of the instantaneous current, a complementer 18 for performing the above-described subtraction, and further from a comparator 19, which shows the instantaneous value of the temperature with the release temperature in the release temperature memory 20 from the associated memory and compares the trigger command memory when the trigger temperature is exceeded 21 activated.

The program flow is in such a computer as

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follows:

Step Mr. 1

The content of the accumulator 15 is on the T-memory l6 transferred (at the beginning this fourth is equal to zero). The complement generator 18 is connected directly to the T-memory and continuously forms the complement of the temperature value.

Step # 2

The complement of T is shifted in place and added to the value of T in the accumulator. This means that the Mert 0.999 is in the accumulator. T available (when using the numerical example mentioned above).

Step # 3

The content of the input register stream 17 is shifted in places by means of the adder IA to the content of the Accumulator 15 is added. Before this addition is carried out, the input register is locked so that any changes of the instantaneous value for the current cannot have any effect during the arithmetic operation. At the end of this The new temperature value is stored in the accumulator 15

Step # 4

In the comparator I9, the new temperature value in the accumulator 15 is compared with the trigger temperature in the associated memory 20. If the release temperature is exceeded, the release command memory 21 is simultaneously set to "release" (eg logical 1). This ends the entire computing cycle; it therefore only consists of a total of k steps; the program now returns to step 1.

If necessary, this program scheme or this configuration can be completed by a number of other facilities. For example, it is possible for 3-phase

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Arrangements with 3 T-memories and 3 input registers for the current to work and dies.e with the only one To process arithmetic unit one after the other. It is also easy to see that there is a difference between the individual T values and a differential release that depends on them is possible. Furthermore, a short-circuit release can be initiated by the instantaneous value of the current in each case with a further short-circuit release limit current value is compared. A staggered release is possible by using a simple one Cycle counter possible. This means that any desired tripping time can be set in ^ t incremental.

ⁿ ie entire arrangement of the digital overcurrent release in cooperation with einenyleistungsschaltenden member, for example a contactor - is shown in Fig. 3. The analog-digital converter 23 is controlled from the main circuit with a suitable current converter 22, which in turn acts on the input register of the digital circuit 2k. The register for the trip command of this digital circuit 2 ^ acts on the amplifier 25, which with its trip contact 26 interrupts the circuit 'of the coil 27 of a contactor. This contactor switches off the main circuit with its main contact 28 in the event of a trip. The input E of the tripping current value and R as a symbol for a reset after tripping is indicated on the digital circuit.

Large-scale integration is preferably used to implement the digital circuit described MOS circuits. The entire expense for the digital circuit to the extent described can be easily achieved on a single chip. The analog-to-digital converter can optionally also be implemented using MOS technology be. Advantageously, discrete technology is used for the amplifier 25 because the required power not with the small power levels of MOS technology

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are easy to implement. Basically, the But the idea of the invention also in a different way use:

In larger control systems are already in many cases Process computer used, which can easily take over the above-described logical sequence. The trigger device consists in this case only of the current converter, the analog-digital converter, the output amplifier and suitable interfaces between these and the computer.

The desired function of the digital circuit described does not necessarily have to be implemented in the form described above; other solutions are also conceivable. For example, the temperature of the bimetal can be simulated using a straight-ahead counter. In a frequency divider, a number of divider frequencies are made available from the clock frequency, which are used to count up the temperature counter depending on the level of the current. The simultaneous cooling is effected by counting down. The downward counting takes place at a higher frequency, the closer the counter reading approaches the preselected trigger counter reading. This method requires a relatively coarse graduation of the tripping characteristic, but could be cheaper for simple tasks than the computer solution described above. Further details of the configuration of a digital circuit in the form of a counter shown in Fig. K. From an analog-digital converter 31, the current value is signaled to the logic part in a few relatively coarse steps. The clock delivers a frequency to the frequency divider, which can consist of the mains frequency, for example, and a large number of partial frequencies are available at the output of the frequency divider. From these frequencies, a frequency is selected by means of the logic logic 32 depending on the level of the current, which for the

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Up counting of the counter 33 leads. It can count up expediently done by the rising edge of the clock pulse. The counter reading is the linkage logic also signaled the countdown pulses from it using the frequency divider 3 ^ and of the clock generator 35, the falling edge is preferably used for counting down. To this Way it is possible to control the counter so that. the counter reading is an image of the temperature. In the steady state the counter reading does not change, i.e. every up counting step is immediately followed by a down counting step. the Triggering is then signaled when the preselected count is reached.

This device can also be implemented with integrated circuits. In some cases, commercially available TTL circuits are used, which may allow a very inexpensive solution.

An electronic overcurrent release of the type described can be produced in various variations. So you can build the release in one or three phases. In the three-phase version, differential tripping can be used be provided. In addition, both the single-phase and the three-phase version can trigger a short-circuit be provided with an adjustable delay time.

Claims

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Claims (5)

231010 Licentia Patent-Verwaltungs-GmbH 6 Frankfurt Alain, Theodor-Stern-Kai 1 SGN-72/22 Frankfurt / Main, February 28, 1973 Wei / hs Claims (1 ·! Electronic overcurrent release for the protection of motors, lines, systems, etc. for cooperation with known power switching elements such as contactors, circuit breakers, motor protection switches and the like, characterized in that a digital circuit is available which leads to a tripping decision in the event of an overcurrent . 2. Electronic overcurrent trip device according to claim 1, characterized in that the logical structure of the digital circuit is designed as a micro computer, ie a control unit, some of the data memory, an arithmetic unit lind includes input and output devices. 3 · electronic overcurrent release according to Claim 1, since by in that the digital circuit is constructed in the form of a counter of simulated the temperature to be simulated Uberstroraschutzorgans that its count disproportionately high for electricity is counted up and proportional to the temperature backward. 4. Electronic overcurrent release according to claim 1 and 2 or 3 » characterized in that highly integrated electronic circuits - for example in MOS or TTL technology - are used as components. 5. Electronic overcurrent release according to claim 1 and 2, A098A3 / 0007 SGN-72/22 -ar- characterized in that, instead of a special digital circuit, the corresponding circuits of an already existing computer are used and thus the overcurrent release consists only of the input and output members (2 and k in FIG. 3). 409843/0007 Blank page